The present invention relates to a method of manufacturing a photomultiplier tube having a proximity multiplier element.
The essential problem to be solved by any method of manufacturing a photomultiplier tube having a proximity multiplier element, a flat photomultiplier having sheet multipliers or a display tube having a disc of microchannels consists in evaporating the photocathode while in such a tube the distance between the photocathode and the multiplier element, sheet multiplier or microchannels disc is very small, on the order of 0.2 mm. It is known from the technique of manufacturing photomultiplier tubes that a good evaporation leading to a homogeneous photocathode requires a photocathode-multiplier distance at least on the order of the diameter of the photocathode. In order to solve said difficulty it is known, for example, from U.S. Pat. No. 3,026,163, to place the window of the photocathode on the one hand and the body of the tube on the other hand in compartments which are separated but communicate with each other and which are then exhausted. The photocathode is then deposited on the window, then activated, in its compartment and transferred by sliding into the other compartment where it is assembled to the body of the tube and where the sealing takes place. It will be obvious that such a method is extremely laborious and expensive, since in practice only one tube can be treated at a time in the manufacturing apparatus. Moreover, said process requires the constant attention of highly qualified and skilful operators.